To the OP. Jack and remove the wheels. Disconnect the wheel speed sensor(s) from the harness in the wheel well. You'll need a digital volt meter (DVM). Connect the meter leads to the wheel speed sensor - polarity doesn't matter. Select the milivolt range (mV). Spin the hub and observe the meter. You should read between 1 and 5 mV when you spin the hub. No output = a defective and/or dirty sensor. Cheap and effective. Good luck.